1. Field of the Invention
The present invention relates to treating goods. More particularly, the present invention relates to a method and apparatus for fumigating goods, such as foods, live munitions, vehicles, and paper records, using a tarp and floor seal. The invention also relates to cooling goods, particularly for storage purposes or after fumigation or treatment. Even more particularly, the present invention concerns fumigation of fruit using methyl bromide gas in a sealed tarp enclosure.
2. Description of the Prior Art
Historically, it has been important to fumigate commodities that are imported into one country from another to kill pests that are not native to the receiving country and that therefore pose a threat to its agriculture. Until recently, fumigation was most often accomplished using methyl bromide gas. While many uses of methyl bromide have been curbed by environmental laws, quarantine fumigation of perishable agricultural products, especially fresh fruit, will continue into the future.
Fruits and produce are normally transported under refrigeration to slow the metabolic processes associated with ripening and decay. In particular, fruit must be warmed to about 40° F. for fumigation, since methyl bromide boils at 38.5° F. and must be used in the gaseous state to be effective.
Fumigation is accomplished by sealing the fruit or produce in an enclosure and filling the enclosure with methyl bromide at a sufficient concentration and temperature, and for a sufficient period of time, to kill the target pest. The fruit is then removed from the enclosure to a cold storage facility to slowly reduce the temperature of the fruit to around 32° F. This cooling process can take as few as two to three days to accomplish, or as many as seven days or more. The actual cooling time depends on the type of packaging material (wooden crates, corrugated cartons, plastic bins, etc.), the configuration of palletized product placed in the cooling chamber, the efficiency of the refrigeration system, target temperature, and other variables. It is known in the art that handling and moving the fruit inherently increases the risk of damage, such as bruising, which lowers the commercial value of the commodity.
One example of fumigating enclosures disclosed in the prior art is U.S. Pat. No. 5,641,463 to Langhart, incorporated by reference herein. Langhart discloses a fumigation tent that includes a suspended frame and tarp, with horizontal pipes surrounding the perimeter of the tarp for rolling up the tarp, and a water-filled hose for sealing the tarp to the floor. A number of fans are used to mix and distribute the methyl bromide gas around the inside of the enclosure. However, this method of sealing the tarp to the floor using water is not widely used, if at all used in the fumigation business, primarily since filling and emptying hoses is time-consuming, cumbersome, and not practical in climates where the water could freeze.
The most widely used method of sealing a tarp to the floor is to weight it down with “sand snakes,” which are elongated bags or sleeves, usually comprised of a vinyl material, that are filled with sand and used to weight the tarp down onto the floor. The bags are typically three to four feet in length and filled with 40-50 lbs. of sand each. In a typical fumigation of 3,500 pallets of commodity, approximately 12 tons of sand must be moved from a storage location to seal the tarp. Then, the same 12 tons of sand must be returned to storage after the fumigation.
These prior art fumigation systems have significant disadvantages. The use of water hoses or sand snakes is often cumbersome, time-consuming and difficult; requiring a number of workers to properly position the weights to adequately seal the tarp to the floor and to prevent gas from escaping. Moreover, if these weighting devices are not properly positioned, or if the tarp is permitted to “bunch,” the methyl bromide gas may escape through resulting openings, causing a safety hazard.
Also, as noted above, the fruit must be heated to at least 40° F. for the fumigation, and then re-cooled. This re-cooling process can take upwards of seven days in these prior art systems, due to the slow rate of thermal transfer between the circulated air and the crated fruit. During this period of elevated temperature, as described above, the product ripens and decays more rapidly than at the appropriate refrigerated storage temperature for the specific commodity in question. The faster the product is re-cooled, the higher the quality and value of the product.
Accordingly, a system is needed that will adequately seal the fumigating enclosure and permit re-cooling after fumigation in the same enclosure; thereby minimizing manual manipulation of the product. Such a system will greatly increase the efficiency of both the fumigation and re-cooling process of perishable products over prior art systems, and will enhance the quality and value of the product being treated by fumigation, or by cooling, or by both processes.